20 
was done b}^ this insect. Professor Cordley has succeeded in making 
some observations upon this leaf-feeding habit which are of great 
value. In a recent letter to the writer he details his experiences as 
follows: 
It was found on June 4 that these eggs had hatched and nearly all of the larv;u were 
dead. Two of them, however, had fed upon the leaves, were yet alive, and had made 
some growth, notwithstanding the fact that the leaves had been taken from the tree 
nearly a month before and were therefore presumably not in the most palatable i o - 
dition. Both larvie were feeding upon the lower parenchyma of the leaf, and one 
had completely covered itself with a web holding pellets of frass. A recently hatched 
larva, mounted in balsam, measured 1.35 mm. in length; the larger of these two 
larv£e at this time measured 1.80 mm. in length and was proportionately stouter. 
Both Avere transferred to fresh leaves, upon which they fed until June 8, when one 
of them disappeared. The other continued to feed until June 11, when it too disap- 
peared. However, I noticed a slight discoloration of the uiidrib of the leaf, near 
where this larva had been feeding, and on carefully opening it found the larva feeding 
as a miner, it having already excavated a tunnel about 15 mm. long. I then examined 
the other leaf, in which I found the larva that had disappeared three days before 
•likewise feeding in the interior of the midrib. The larv{\3 were again transferred to 
fresh leaves, and by the following morning each had again disappeared within a midrib. 
Both larvse continued to feed within tha midribs until June 16, when one of them, 
on being transferred to a fresh leaf, refused to eat and soon died. The other, with 
occasional changes to new pastures, continued to thrive until June 25, when it was 
plump and active and apparently in the best of health and spirits. Unfortunately 
I was then absent from the laboratories for some days, and when I returned the 
larva was dead. I believe that with careful attention it could have been brought to 
maturity on a diet of leaves alone. When one considers that it lived and grew for 
more than three weeks upon leaves that had been severed from the tree sometimes 
for several days, and that it was apparently more thrifty between June 16 and 25 
than in the earlier days of its existence, one must acknowledge that, while the proof 
is by no means positive, the indications are that codling moth larvje may fully 
develop on a diet of perfectly fresh apple leaves without ever having tasted fruit. 
(See PL II, fig. 1.) 
The writer has man}^ times taken larvae from apples and placed 
them upon leaves in cages and bottles. It was found that the larvae 
would fasten the leaves together with silk and eat holes in them; but 
on account of lack of attention no larvie were bred to maturity. The 
writer believes, and agrees with Professor Cordley in believing, that 
the larvas with proper care can be brought to maturity on the leaf 
diet alone. 
This (][uestion of the leaf -feeding habit of the codling moth is one of 
the most important questions in the life history of the insect, and 
should especiall}^ commend itself to entomologists for future investi- 
gation, since not only will it give us a very important biological fact, 
but it will also prove very definitely how sprajdng is efiective against 
the insect. 
It has often been recorded that larvae gnaw cavities in rough rotten 
wood, bark, cloth, paper, and other places where the}^ spin cocoons, 
and the bits of these substances incoi-porated in the cocoons. From 
